The invention relates generally to the field of digital color management and, more specifically, to creating an abstract profile that digitally reproduces the color of an optically created image on a digitally created image.
In traditional photography, photo processing labs have a printing apparatus that optically creates prints. Typically, film containing negative images is passed under a light source so that the light passes through the film and onto a light-sensitive paper, creating a latent image which is then developed by a chemical process. Colored filters interposed between the light source and the paper provide means for adjusting the color balance of the prints.
In contrast, in creating prints digitally, color transforms are used to adjust the colors. A digital printing system typically uses scanners, displays, and printers which have different relationships between their digital values and the corresponding image colors. Color transforms are used to modify the relationship between these digital values and colors to produce accurate, predictable, and aesthetically pleasing prints. These transforms are typically embodied in profiles of a color management system.
While presently known and utilized color management systems often provide significant improvement in color reproduction in digital imaging systems, they have certain shortcomings, particularly with respect to reproduction of images from photographic negatives. They do not provide convenient and reliable means for duplicating the appearance of an optical print. The optical and digital systems function independently so that adjustments made in the optical system are not used in the digital system and vice versa. It is desirable to have the adjustments made optically to be included in the digital process for efficiency in the process of generating images. This would eliminate duplicating the adjustment digitally for which an adjustment has already been created optically.
The prior art of digital color management is primarily concerned with the reproduction at the output of a system of colors of some original version of an image provided to the input stage of the system. While many methods have been disclosed, for example, as in U.S. Pat. No. 5,481,380, none of these methods has addressed the problem of systematically adjusting an image to match an arbitrary aim. This problem is most obvious in the case of producing a viewable image from a photographic negative. A negative is fundamentally a record of exposures of the elements of a scene. It is not designed for direct viewing; the colors are reversed, and there is often an overall orange cast resulting from certain chemically-generated optical features of the photographic system. In short, the negative must first be rendered in some fashion to produce an image suitable for viewing. This is traditionally done by a process in which light is passed through the negative onto paper coated with photosensitive material which, upon chemical development, reverse the colors of the negative and produce a positive image. The present invention teaches a simple method for introducing the result of such an optical process, or indeed of any image forming process, into a digital imaging system as the aim for reproduction of color and tone.
Commonly assigned copending U.S. patent application Ser. No. 09/100,217, which was filed Jun. 19, 1998 and entitled xe2x80x9cMethod for Including Traditional Photographic Calibration into Digital Color Managementxe2x80x9d, addressed some of these issues; however, it was concerned only with color balance changes represented as changes in density of neutrals of a photographic print material. To overcome this limitation, a method is needed for adjusting colors irrespective of the particular medium in which they are expressed or of the devices used for scanning and printing the images.
The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the present invention, a method for incorporating photographic calibration into digital color management having an abstract color transformation profile includes the steps of: (a) generating an optical reproduction from a photographic film containing an image of a target having a plurality of colored and neutral patches; (b) scanning said film in a transmission scanner and generating film image data; (c) transforming the film image data to data in a first profile connection space using the color management system; (d) reading said optical reproduction and generating reproduction image data; (e) transforming the reproduction image data to data in a second profile connection space using a color management system; and (f) computing an abstract profile to transform said data in the first profile connection space to data in the second profile connection space.
In a preferred embodiment, the optical reproduction generated in step (a) is an optical print and the reading of said optical reproduction in step (d) comprises scanning the optical print on a reflection scanner.
The advantage of the invention is that it addresses the problem of systematically adjusting an image to match an arbitrary aim, particularly where that aim is to produce a viewable image from a photographic film, such as a negative. The invention thus provides a convenient and reliable means for duplicating the appearance of an optical print. These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.